CeO sub(2) nanodots embedded in a porous silica matrix as an active yet durable catalyst for HCl oxidation

A unique architecture of CeO sub(2) nanodots embedded in a porous SiO sub(2) matrix (CeO sub(2)iO sub(2)) was successfully fabricated by a spontaneous deposition strategy and evaluated in the recycling of Cl sub(2) from HCl oxidation. The nano-sized CeO sub(2) particles with a narrow size distribution (2-4 nm) were uniformly dispersed in the amorphous SiO sub(2) matrix. Based on the characterizations from various techniques, including XRD, SEM/(HR)TEM, H sub(2)-TPR, Raman, and XPS, it was revealed that the CeO sub(2) nanodots in the SiO sub(2) matrix exhibited a significant "size effect", with characteristics such as a considerably high concentration of Ce super(3+), a high fraction of oxygen vancant sites, and a notably enhanced oxygen reducibility, which all affect oxygen activation and surface Cl desorption. The current CeO sub(2)iO sub(2) catalyst shows superior activity (1.60 g sub(Cl) sub(2)g sub(cat) super(-1) h super(-1)) and good durability (an on-stream time of 100 h at 703 K). The isolation of fine CeO sub(2) nanodots by the SiO sub(2) matrix is a key factor in the inhibition of sintering of CeO sub(2) entities. Kinetic measurements indicate that catalytic activity is more dependent on the O sub(2) partial pressure than that of HCl, suggesting that enhancement in oxygen adsorption and surface Cl desorption is crucial for improving the catalytic activity.